Air conditioning system



Oct. 24, 1939. sPAAN 2,177,602

AIR CONDITIONING SYSTEM 7 7 Filed May 11, 1936 5 Shegts-Sheet l POWER SUPPLY I HEAT EXOHAN GER COLD WATER ST TANK COLD 5 WATER TAN K TO BOILER a C00 LER CONDENSER DENSER Oct. 24, 1939. J. H. SPAAN AIR CONDITIONING SYSTEM Filed May 11, 1936 5 Sheets-Sheet 2 MMAAOMFZOu TEE MU IONCIZOU PC9231 M03;

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Get. 24, 1939. J.'H. SPAAN AIR CONDITIONING SYSTEM Filed May 11, 1936 5 Sheets-Sheet I5 Oct. 24, 1939. .1. H. SPAAN AIR CONDITIONING SYSTEM Filed May 11, 1956 5 Sheets-Sheet 4 J mm A m@@ mmm www w ms mom vows N John H Sfa an O 1939. J. H. SPAAN 7,602

AIR CONDITIONING SYSTEM Filed May 11, 1936 I 5 Sheets-Sheet 5 TO FROM COOL! NG COOLIN G TOWER TO I \QUID RECE\VER FROM HEAT EXCHANGERS AND COLD WATER STORAGE. TANKS To A\R CONDITIONERS John H Spa/a1;

Patented Oct. 24, 1939 UNITED STATES AIR CONDITIONING SYSTEM John H. Spaan, Oklahoma City, Okla., asslgnor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application May 11, 1936, Serial No. 79,091

39 Claims.

The present invention relates to air conditioning systems by means of which the conditions in a space or a plurality of spaces may be controlled both in warm weather and in cold weather. The 5 invention is directed not only to the specific man ner of controlling the conditioning of the air itself but further relates to the combination of several such systems into a single large system in which the supplies of cooling and heating mediums are controlled in new and novel manners.

One of the objects of the present invention is the provision of an improved system of controlling the circulation of a temperature changing fluid, such as water, which is utilized to vary the temperature of air to be conditioned.

More specifically, the present invention has for an object the provision of a circulation controlling system in which anyone of a plurality of circulating devices may be utilized to circulate a temperature changing fluid and providing means by which another of such circulating devices is placed in operation when the temperature of the circulating fluid returning from the devlcesto be heated or cooled thereby reaches a predetermined value.

Another object of the present invention is the provision of a cooling system for cooling a circulating medium in which the cooling apparatus cannot be placed in operation unless the fluid 0' medium is in actual circulation.

More specifically, it ,is an' object of the present invention to permit the operation of a cooling apparatus only in the event the pressure of a circulating medium which is cooled by the cooling apparatus changes from its static value there'- by indicating that the fluid to be cooled is actually in circulation,

Another object of the invention is the provision of a cooling system of I the type in which part of the cooling apparatus, such as the condenser of a mechanical refrigeration system, is cooled by means of the use of circulating a cooling fluid therethrough, such as circulating water through such a condenser, and in which the cooling apparatus is rendered inoperative after a time period if, in-the meantime, the circulation of such cooling fluid has not commenced or, if during the operation of the cooling apparatus, the flow of the cooling liquid through the condenser is not maintained in sufficient volume to accomplish its.

the event the pressure of the condenser cooling water is not changed from a value equal to the static pressure.

A further object of the invention is the provision of a cooling system that includes a plurality of cooling apparatuses and arranging the system in such a manner that the cooling apparatuses are brought into operation alternately upon consecutive demands for cooling. In other words, upon a call for cooling, one of the cooling apparatuses is brought into operation and remains in operation until such call for cooling is satisfied and upon the next subsequent call for cooling the other cooling apparatus is brought into operation and remains in operation until the call for cooling is satisfied.

A further object of the invention is the provision of a cooling system in which a pair of cooling apparatuses are alternately brought into operation upon consecutive demands for cooling, and in which both cooling apparatuses are brought into operation upon an increased demand for cooling. Stated in another way, it is anobject of this invention to provide a plurality of cooling apparatuses, both of which can be placed in operation at the same time in the event both cooling apparatuses are needed in order to obtain the desired cooling action, but in which if the demands for cooling are sufficiently small that only one cooling apparatus need be used then these cooling apparatuses are alternately operated upon consecutive demands for cooling.

Another object of the invention is the provision of an air conditioning system in which the supply of air to be conditioned to a plurality of conditioners is provided in a single large room or enclosure to which return air and fresh air is supplied.

Another object of the invention is the provision of a large room or enclosure to which return or fresh air is supplied under the control of suitable automatic controls, together with a plurality of air conditioning devices, each of which then receives its supply of air for conditioning from this central or single room or enclosure.

A further object of the invention is the provision of a novel electrical damper operating system wherein the dampers are too numerous or too heavy to be operated by a single electrical motorized mechanism wherefor a plurality of such mechanisms are necessary.

More specifically, it is an object of this invention to move a first damper from a first position to a second position by an electrical motor means which requires an appreciable time to so move theflrst damper, and to have such motor means in turn operate mechanism which causes a second motor means that controls a second damper to exactly follow the motor of the first motor means. In this manner, both dampers are operated substantiallysimultaneously by the use of commercial equipment available on the market.

A further object of the invention is to control dampers in an air conditioning system in such a manner that they are moved from a position permitting a maximum supply of air to pass therethrough to a position in which a minimum supply of air is allowed to pass therethrough and back to a position in which a maximum amount of air is allowed to pass therethrough as the outdoor temperature rises from a relatively low value, passes through an intermediate value, and then rises to an extreme or high value.

A further object of the invention is the provision of a combined cooling and dehumidifying system in which the dehumidifying action is ob tained by decreasing the volume of air flowing through a cooling coil wherefor its speed of flow is reduced and itis cooled to a greater extent so as to remove more moisture therefrom.

More specifically, an object of the invention is the provision of an air conditioning system having a cooling coil only part of which is normally used for cooling puposes, a small amount of air being allowed to flow through the other portion thereof at a slow rate so as to obtain a high degree of cooling and dehumidiflcation upon a. demand for dehumidificationa Another object of the invention is the provision of an air conditioning system in which auxiliary damper means permits the flow of a small amount of air through a cooling coil upon a demand for dehumidification whereby such small amount of air moves at a slow rate and is cooled to a relatively great extent so as to remove a substantial amount of moisture therefrom.

A further object of the invention is the provision of an air conditioning system in which a plurality of air conditioners are supplied with a temperature changing fluid from a single source and in which the rate of flow of this temperature changing fluid to the various air conditioning devices is changed in accordance with changes in the temperature of the temperature changing fluid as it returns from all of the air conditioncombinations and sub-combinations to be disclosed hereinafter in detail, as well as various combinations of the features set forth above and will be found in the drawings, the detailed description and the appended claims.

For a better understanding of the invention, reference may be had to the following detailed description and the accompanying drawings, in which:

Fig. 1 is a diagrammatic showing of the manner in which the chilled and heated water is supplied for the complete air conditioning system and including the controlling apparatus therefor,

Fig.2 is a diagrammatic showing of the general arrangement of the air conditioning devices and the manner in which a common supply of air to be conditioned is'provided for all of the air conditioning apparatuses,

Fig. 3 is a diagrammatic showing of the control apparatus for that part of the apparatus shown'in Fig. 2 by means of which the common supply of air to be conditioned is provided for the various air conditioning devices,

the various air conditioning devices utilized in the present invention in any manner desired, the

present invention includes a specific manner of providing such a supply of chilled and heated water. Referring first to Fig. 1 of the drawings, chilled or heated water is supplied to the air conditioning devices by means of a main delivery pipe indicated at Connected to this main delivery pipe in is a pair of branch delivery pipes II and 2 which are respectively connected to the outlets of a pair of circulating pumps 3 and M which are respectively driven by electric motors I5 and I6. The inlets of the pumps l3 and H are respectively connected to branch inlet pipes l1 and I8 which in turn communicate with a main inlet pipe l9. After the heated or chilled water has passed through the various air conditioning devices in a manner to be explained hereinafter, it is returned by a main return pipe 20. The main inlet pipe I9 and the main return pipe 20 are respectively connected to the outlet and inlet of a heat exchanger 2| by means of pipes 22 and 23. Located in the pipe 22 is a manually operable shut-off valve 24 and a similar manually operable shut-off valve 25 is located in the pipe 23. It will be apparent that by opening these valves 24 and 25, the heat exchanger 2| can be placed in communication with the circulators l3 and I4 and with the main return pipe 20 and that by closing these valves 24 and 25 it is impossible for any water to flow to or from the heat exchanger and into or out of main inlet pipe H3 or the main return pipe 20.

The heat exchanger 2| is utilized to provide heated water or steam during cold weather. In the instant invention, this is accomplished by providing the heat exchanger 2| with a supply of steam through the medium of a steam supply pipe 26, under the control of a modulating or proportioning valve 21. This supply of steam may be obtained in any desirable manner either from an individually controlled boiler or from a central power station, and the pipe 26 may be further provided with a manually operable valve 28 for the purpose of preventing the flow of steam to the heat exchanger 2|. After the steam has passed through the heat exchanger 2| it is returned to the individual boiler or disposed of in any desirable manner, as by permitting it to flow to a drain by means of a pipe 29.

Modulating or proportioning valve 21 may take any desired form and may be controlled in any desired manner. As herein shown, this valve includes a valve stem 30 which is connected to a rack 3|- Cooperating with the rack 3| is a pinion 32 which is carried by the main operating shaft 33 of a motor mechanism 34. This motor mechanism 34 is supplied with power by means of line wires 35 and is controlled by a thermostatic mechanism generally indicated at 36.

The thermostatic mechanism 36 includes a bell crank pivoted at 31 and having a control arm 38 and an actuating arm 39. The control arm 38 cooperates with a control resistance 40 which is connected to the motor mechanism 34 by meansof wires 4| and 42. The control arm 38 is likewise connected to the motor mechanism 34 by means oil a wire 43. The actuating arm 88 is positioned by a' bellows 44, one end 0! which. en-' '48, the connection being by means oi a connect- The bellows, bulb and connecting.

ins tube 41. tube are charged with a suitable volatile fluid, as is well known in the art, by means of which varisponse to temperature changes at the controlling bulb 46. A coiled spring 48 has one of its ends attached to the actuating arm 38 and its other end attached to the support 45 and serves to oppose the variable pressures built up in the bellows 44.

This thermostat 36 may respond to any desired temperature and is herein shown as having its controlling bulb 46 located in heat exchange relationship with the pipe 22 which leads from the heat exchanger 2I and connects to the main inlet pipe I8 for the circulators I3 and I4. The arrangement oithis thermostat is such that substantially 6 F. are required to cause the control arm 38 to completely traverse the control resistance 48 and the setting is such that this 6 temperature is from 132 F. to 138 F. The manner in which such a potentiometer type thermostat may control a motor mechanism such as the motor mechanism 34 to position a valve is now thought to be well known in the art. This mechanism may take the electrically balanced form as will be described hereinafter in connection with the control of certain other phases of the air conditioning system, or may be of the mechanical follow-up type such as disclosed in Lewis L. Cunningham Patent No. 1,889,972 granted February 5, 1935. In any event, the thermostat 36 variably' positions the valve 21 through the medium of the motor mechanism 34 so as to maintain the temperature of the hot water leaving the heat exchanger between 132 F. and 138 F. With the parts in-the position shown, the apparatus is operating on a cooling cycle, whereior the manually operable valves 24 and 25 are closed as is the manually operable valve 28. Therefore, no steam is being supplied to the heat exchanger 2| and the temperature of the controlling bulb 46 corresponds to the surrounding atmosphere which, of course, would be lower than 132 F. As a result, the actuating arm 88 is engaging the extreme right-hand end of control resistance 48 and the proportioning valve 21 is completely open. However, since the manually operable valve 28 is closed no steam is flowing to the heat exchanger Inorder to supply chilled water to .the air conditioning system, a tube and shell cooler 58 is provided. This cooler connects to a pair of cold water storage tanks 5| and 52 by means of pipes 53. These cold water storage tanks SI and 52 in turn connect with the main inlet pipe I8 for the circulating pumps by means of a pipe 54 which is provided with a manually operable valve 55. The main return 28 is connected to the cooler 58 by a pipe 56 and a manually operable valve 51 is included in this pipe 56. As in the case, of the heat exchanger 2|, these manually operable valves 55 and 51 make it possible to valve oi! the cooling system or to place it in communication with the air conditioning devices. As indicated above, the system is operating under a hot weather cycle so as to provide chilled water whereior the valves 55 and 51 are in their open positions. The purpose of the cold water storage tanks 5| and 52 is to provide a relatively large supply of cold water which is capable of taking care oi any sudden or unusual demands on the cooling system.

The water in the'cooler at is adapted to b cooled by means of a mechanical refrigeration system which includes a pair of compressors 88- and 6| which are respectively driven by com--' *Dressor motors-62 and 63. The hot gaseous reable pressures are created in the bellows in reirigergnt compressed bythe compressor 68 is led to a condenser 84 by means of a pipe 65. Similarly, thehot gaseous refrigerantcompressed by the compressor 6| is led to a condenser 86 by means oi. a pipe 61. The hot refrigerant is cooled and liquefied by these condensers in the usual manner and is then discharged into a liquid re ceiver 68 by means of connecting pipes 68. From this liquid receiver the refrigerant passes to the cooler 58 through a pipe 18 which is provided with an expansion valve H. The refrigeraht is expanded in the cooler 58 through the medium of the usual expansion coil and cools the water contained therein. The refrigerant then returns to the compressors 68 and 6| by means of pipes indicated at 12.

The condensers 64 and 66 are herein shown as being of the water cooled type to which water is delivered from a cooling tower. 13 by means of pipes 14. The return water from the condensers 64 and 66 is led to a condenser water pump 15 by means of pipes 16. This pump is driven by a condenser pump motor 11 and the water is forced by this pump 15 through a pipe 18 which communicates with the spray 18 of the cooling tower 13.

The circulating pump motors l5 and It are electrically controlled by a system which will now be described. The motor I3 is controlled by a relay which includes a relay coil 88 that positions an armature 8| which in turn operates switch arms 82 and 83. Upon energization of the relay coil 88, the switch arms 82 and 83 are moved into engagement with contacts 84 and 85, respectively. In a similar manner, the circulating pump motor I6 is controlled by a relay that includes a relay coil 86 which operates an armature 81 that posi tions a pair of switch arms 88 and 88. Upon energization of the relay coil 86 the switch arms 88 and 88 are respectively moved into engagement with contacts 88 and 8|.

The energization ofthese relay coils 88 and 86 is controlled by three manual switches 82, 83, and 84 by a thermostatic switch generally indicated at 85. The three manual switches 82. 83 and 84 are of the single-pole, single-throw type and need no further explanation. The thermostatic switch 85 includes a switch carrying arm 86 which is pivoted at 81 and carries a mercury switch 88. This switch carrying arm 86 is positioned by a bellows 88 which is connected to a controlling bulb I88 by means of a connecting tube I8 I. The bellows, bulb and tube are charged with volatile fluid whereior variable pressures are created in the bellows 88 upon changes in the temperature at the controlling bulb I88. A' spring I 82 has one of its ends secured to the switch carrying arm 86 and its other end secured to a support I83 and serves to oppose the variable pressures created in the bellows 88. As shown, one end of bellows 88 engages the switch carrying arm Y86 and its other end is secured to the support I83.

This thermostat 85 may respond to any desired temperature and is herein shown as responding to the temperature of the water which is being returned to the cooler 50. In other words, this thermostat 95 responds to the temperature of the Water as it leaves the various air conditioning devices. The arrangement is such that mercury switch 98 is in the open circuit position in which it is shown in Fig. 1. Whenever the temperature of this returned chilled water is at or below 41 F., and is moved to closed position whenever the temperature of this water rises to or above 43 F.

Either relay coil 80 or 86 can be energized by closing its associated manual switch 92 or 93. With the parts in the position shown in Fig. 1, the manual switch 92 is closed wherefor-the relay coil 80 is energized by a circuit as follows: Line wire I05, wire I06, wire I01, manual switch 92, wire I08, wire I09, and relay coil 80, to ground I I0, it being noted that the other line wire II II is likewise connected to ground IIO. Since relay coil 80 is energized, the switch arms 82 and 83 are engaged with contacts 84 and 85. Engagement of switch arm 83 with contact 85 energizes the circulating pump I5 by a circuit as follows: line wire I05, wire I06, wire II2, wire II8, wire II4, wire II5, contact 85, switch arm 83, wire II6, circulating pump motor I5 and ground H0. The circulating pump I5 is, therefore, in continuous operation. Now, in the event the manual switch 94 is also closed as shown in Fig. 1, then the thermostat 95 is operative to energize the other relay coil 86 if the temperature of the return water rises to 43 F., so as to close the mercury switch 98. Assuming that the return water temperature does rise to this value, then the relay coil 86 will be energized by a circuit as follows: Line wire I05, w'ire I06, wire II2, wire II3, wire II1, manual switch 94, wire II8, the left-hand electrode of mercury switch 98, the middle electrode thereof, wire I I9, switch arm 82, contact 84, wire I20, wire I2I, relay coil 86 and ground IIO. Energization of relay coil 86 moves switch arms 88 and 89 into engagement with contacts 90 and 9I wherefor circulating pump motor I6 isenergized as follows: Line wire I05, wire I06, wire II2, wire II3, wire II4, wire I22, contact 9i, switch arm 89, wire I23, circulating pump motor I9, to ground IIO. In this manner, when the temperature of the returned chilled water rises to some undesirable high value, such as 43" F., thereby indicating that the load on the air conditioning devices is relatively heavy, the other circulating pump is brought into operation in order to increase the flow of chilled water to the air conditioning devices whereby to take care of this excessive load, In the event the temperature of the returned chilled water drops to 41 F., mercury switch 98 returns to the position shown in Fig. 1 and the circuit for relay coil 86 is interrupted thereby causing deenergization of the circulating pump motor I6.

If the manual switch 92 be opened and the manual switch 92 be closed instead, then the relay-coil .86 is continuously energized by a circuit as follows: Line wire I 05,'wire I06, wire II2, wire I24, manual switch 93, wire I25, wire I2I, and relay coil 86 to ground H0. The circulating pump motor I6 is therefore continuously energized under these conditions. If the manual switch 94 is still closed and if the temperature of the return chilled water should rise to 43 F., then the relay coil 80 is energized as follows: Line wire I05, wire I06, wire II2, wire II3, wire II1, manual switch 94, wire II8, mercury switch 98, right-hand electrode thereof, wire I26, switch arm 88, contact 90, wire I21, and wire I09 to relay coil 80 and ground II 0. Such energization of relay coil 80 energizes the circulating pump motor I5 by the circuit set out above.

From the foregoing it is seen that either circulating pump motor I5 or I6 can be placed into continuous operation by means of closing either the manual switch 92 or the manual switch 93. In addition, in the event the manual switch 94 is closed, the other circulating pump motor will be energized whenever the temperature of the returned chilled water rises to 43 F., irrespective of which one of these motors is manually operated continuously. Also, if both manual switches 92 and 93 are closed then both circulating pump motors I5 and I6 are operated continuously irrespective of the temperature of the returned chilled water. This arrangement makes it possible to even up the wear and tear on both circulators by placing either of them in continuous operation and permitting the other to be automatically brought into operation. During cold weather it has been found that in this particular system suflicient hot water is supplied to the air conditioners irrespective of how cold it gets outside by only operating one circulator. Therefore, the manual switch 94 should be left open during the winter operation and the desired circulator can then be placed in operation by closing one or the other of the manual switches 92 or 93.

In the event the switch 94 is left closed in the winter, during which time the cooler 50 is valved off by closing of the valves 55 and 51, it will be apparent that the temperature at the control bulb I will be that of the surrounding atmosphere which under all usual conditions would be above 43 F., wherefor both circulating motors I and I6 will be in continuous operation even though only one of the switches 92 or 93 is closed.

The compressor motors 92 and 63 are controlled, in a manner which will now be explained,

in accordance with the temperature of the water leaving the cooler 50. In order to control these compressor motors in a particular manner, which will become clear hereinafter, three thermostats responsive to the temperature of the chilled water are provided. These thermostats are generally indicated at I30, I3I, and I32.

The thermostat I30 includes a switch carrying arm I33 which is pivoted at I34 and supports a mercury switch I35. This switch carrying arm I33 is positioned by one end of a bellows I36, the other end of which is secured to a support I 31.

'The bellows I36 communicates with a controlling bulb I38 through a connecting tube I39. The bellows bulb and tube are charged with a suitable volatile fluid so that variable pressures are created in bellows I36 upon temperature changes at the bulb I38, and the variable pressures thus created at the bellows I36 are opposed by a coiled spring I40 which has one of its ends secured to the switch carrying arm I33 and its other end secured to the support I31.

The thermostat I3I is a substantial duplicate of the thermostat I30 and includes a switch carrying arm I M which is pivoted at I42 and supports a mercury switch I43. This arm is positioned by a bellows I44 that has one of its ends secured to a support I45. The bellows I44 is connected to a controlling bulb I46 through a connecting tube I41, the bellows, bulb and tube being charged with a suitable volatile fluid. A coiled spring I48 opposes the variable pressures created in bellows I44 as a result of temperature changes in the bulb I46.

The thermostat I32 is likewise generally sim- 15 llar to the thermostats I30 and ISI. This thermostat includes a switch carrying arm I49 which is pivoted at I50 and supports a mercury switch II. This switch carrying arm I49 is positioned by a bellows I52 which has one of its ends connected to a support I53. The bellows I52 communicates with a controlling bulb I54 through a connecting tube I55 and a coiled spring I56 opposes the variable pressures created in bellows I52 upon temperature changes at the bulb I54.

As indicated above, these three thermostats I30, I3I, and I32 respond to the temperature of the chilled water and for this purpose the bulbs I38, I46 and I54 of'these thermostats have been shown as positioned in heat exchange relationship with the pipe 53 which is connected to the outlet of the cooler 50. The thermostat I30 is arranged in such a manner that the mercury switch I35 thereof moves to closed circuit position whenever the temperature of the chilled water rises to or above 42 F., and moves to open position whenever the temperature of this cooled water falls to or below 34 F. The thermostat I3I is arranged so that its mercury switch moves to closed circuit position whenever the temperature of the chilled water rises to 39 and moves to open position whenever the temperature thereof falls to 35 F. The mercury switch I5I of the thermostat I 32 is of the double circuit type which closes a circuit regardless of which way it is tilted.- This mercury switch can operate at any temperature within the temperature limits of the thermostat I3I for reasons which will become apparent hereinafter. For the purpose of this explanation, it will be assumed that the mercury switch I5I is in the position shown in Fig. 1 in which its left-hand electrodes are closed whenever the temperature of the chilled water is at or below 36 F. Whenever the temperature of this water rises to or above 38 F. the mercury switch I5I is tilted to the opposite position in which its right-hand electrodes are closed.

The control system for the compressor motors 62 and 63 additionally includes certain safety controls in the form of a pressure responsive switch generally indicated at I60, a second pressure responsive switch generally indicated at I6I and a thermal cut-out switch. The thermal cut-out switch includes a pair of switch arms I62 and I63 which are normally in engagement and are so held in engagement by a bimetallic element I64. This bimetallic element I64 is adapted to be heated by an electrical heating element I65. The arrangement is such that if the heating element I65 is energized for a predetermined length of time the bimetallic element I64 is raised in temperature sufliciently that it goes far enough to the right to move out from under the end of switch arm I63. This permits switch arm I63 to separate from switch arm I62 to open the circuit therebetween. This circuit then can only be again completed by manually moving these switch arms I62 and I63 into engagement. Thermal switches of this type are well known in the oil burner art by the name of "safety switches and the thermal switch of the present invention may well take the form shown in Frederick S. Denison Patent No. 1,958,081 granted May 8, 1934.

The pressure responsive switching mechanism I 60 includes a switch carrying arm I66 which is pivoted at I61 and carries a mercury switch I68. This switch carrying arm I66,is positioned by a bellows I69 which is supported by a support I10. This particular pressure responsive switching mechanism I60 responds to the pressure in the main inlet pipe I9 to the circulating pumps I3 and I4. For this purpose the bellows I99 is connected to this pipe I9 by means of a pipe I1I. The pressures to which the bellows I69 is thus subjected are opposed by a coiled spring I12. The purpose of this pressure responsive switching mechanism I60 is to determine whether or not either one of the circulators I3 and I4 is in operation. When neither of these circulators is in operation there will be a predetermined pressure in the pipe I9 or a static pressure which depends entirely upon the head or water in the system. In the particular system to which the present invention was applied this static head was substantially 42 pounds. Now, it will be evident that upon operation of either one of the circulators I3 and I4, there will be a decrease in pressure in'the pipe I9 which is on the suction side of the pumps I3 and I4. The switching mechanism I60 is, therefore, so arranged that the mercury switch I68 thereof is in open circuit position whenever the pressure in pipe I9 is at or above the static head of the system and moves to closed position whenever the pressure in this pipe is reduced therebelow. It is, therefore, evident that the mercury switch I68 will be open whenever neither circulator is operating. Also, it will be apparent that mercury switch I 68 will close in the event either of these circulators is operating. The mercury switch I68, therefore, by its position gives an indication as to whether or not the Water is being circulated to the air conditioning devices.

The pressure responsive device I6I is similar to the device I60 and includes a switch carrying arm I13 which is pivoted at I14 and carries a mercury switch I15. This switch carrying arm I13 is positioned by a bellows I16 which has one end secured to a support I11. This bellows I16 responds to the pressure on the inlet or suction side of the condenser. water pump and is, therefore, connected to the pipe 16 by means of a pipe I18. The pressure thus produced in the bellows I16 is opposed by a coiled spring I19. In this particular system the static head of the condenser water circuit is substantially 50 pounds. This is slightly higher than the static head in the circulating system by reason of the cooling tower being at a higher point than are any of the air conditioning devices. The pressure responsive switching mechanism I6I is, therefore, arranged so that mercury switch I15 is in the open circuit position shown whenever the pressure on the inlet or suction side of the condenser water pump 15 is at or above 55 pounds, and is closed whenever this pressure is lowered. It will, therefore, be evident that mercury switch I15 is open unless the condenser water pump 15 is in operation.

The control system for the compressor motors 62 and 63 further includes five relays which respectively have operating coils I85, I86, I81, I88, and I89. The relay coil I85 operates an armature I90 which in turn controls switch arms I9I and I92. Upon energization of the relay coil I85 switch arms I9I and. I92 are moved into engagement respectively with contacts I 93 and I94. Similarly, the relay coil I86 controls an armature I95 which positions a pair of switch arms I96 and I91. Upon energization of the relay coil I86 these switch arms I96 and I 91 respectively move into engagement with contacts I96 and I99. The relay coil I81 operates an armature 200 which moves a single switch arm l into engagement with a single contact 202 when the relay coil I8! is energized. In a similar manner, the relay coil I88 controls an armature 203 which moves a single switch arm 204 into engagement with a single contact 205 upon energization of the relay coil 2I1 is secured. This motor mechanism 2I5 is of a type well known in the art which makes successive half revolutions of, 180 degrees under the control of the mercury switch I5I. Electrical power is furnished to this motor mechanism 2I5 in a manner which will be set forth in detail hereinafter. The crank 2I1 is connected to one end of a cable 2I8 which is partially wound about a disc 2I9 and is secured thereto as indicated at 220. A coiled spring 22i has one of its ends secured to the disc 220 and its other end secured to a suitable support 222 and serves to bias the disc 2 I9 to the position shown. This disc 2 I9 is loosely mounted upon a shaft 223 which carries a ratchet 224. Pivotally carried on the disc 2I9 are a plurality of pawls 225 which are adapted to cooperate with the ratchet 224 so as to cause counterclockwise rotation thereof upon counter-clockwise rotation of the disc 2I9. As is usual in such ratchet constructions, the ratchet 224 is not moved, but remains stationary, upon clockwise movement of the disc 2I9. The shaft 223 operates a contact arm 226 which is adapted to engage contacts 22'Iand 228. Assuming that power is available for the motor mechanism M5, and with the parts in the position shown in Fig. 1, if the mercury switch I 5| of the thermostatic mechanism I32 is tilted to the opposite position in which its right-hand electrodes are bridged, then the crank 2I1 will be driven in a counter-clockwise direction through 180 degrees. As the crank arm 2I1 starts this counter-clockwise movement, it will pull upon the cable 2 I8 and cause a counterclockwise rotation of the disc 2I9. By properly correlating the radius of the disc 2I9 with the length of the crank arm 2I1, the disc 2I9 is moved a half revolution in counter-clockwise direction by the time arm 2I1 has moved through a quarter revolution, or is pointing in a downward direction. Such a half revolution of the disc 2I9 causes the shaft 223 to be driven through a half revolution by means of the pawls 225 and ratchet 224. This causes movement of switch arm 226 so that it disengages contact 221 and moves into engagement with contact 228. Now, as the crank 2I1 completes the other quarter of its half revolution, or goes from its downwardly pointing position to the horizontal position in which it points to the right, the spring 22I returns the disc 2I9 to the position shown in Fig. 1. Y

During this movement of the disc 2I9 the shaft 223 remains stationary by reason of the ratchet and pawl connection between theshaft and the disc. It will thus be seen that an increase in the temperature to which the thermostat I 32 responds to 38 F. causes switch arm 226 to disengage contact 221 and move into engagement with contact 228.

If the temperature now falls to 36 F. so that mercury switch I5I returns to the position shown in Fig. 1, then the motor mechanism 2I5 will move crank 2I1 through another half revolution in counter-clockwise direction. During this half revolution of the crank 2I1, the disc 2I9 remains ment with contact 221. If the temperature then again falls to 36 F..the crank 2I1 will again return to its original position but the shaft 223 will remain stationary. In other words, the switching mechanism 226'22'|--228 is operated to a new position every. time the temperature rises to 38 F. after it has fallen to 36 F. but is never operated upon temperature fall.

As has been brought out above, the circulator I3 is in operation by reason of the fact that manual switch 92 is closed. The pressure in pipe I9 should, therefore, be such that the mercury switch I68 is closed. The mercury switch I35 01' the thermostat I30 is shown open, which indicates that the temperature of the chilled water is below 34 F. The mercury switch I43 of the thermostat I3I is therefore also open since this mercury switch opens when the temperature of the chilled water falls to 35 F. In addition, the mercury switch I5I of the thermostat I32 has its left-hand electrodes closed since they are closed when the temperature of the chilled water falls to 36F. Chilled water is, therefore, being circulated to the various air conditioning devices or other apparatus and after a time period it is obvious that the temperature of the chilled water will rise due to the taking on of heat by the chilled water. When this temperature rises to 38 F. the mercury switch I5I will be tilted so as to close its right-hand electrodes whereupon the contact arm 226 will disengage contact 221 and engage contact 228 in the manner heretofore explained. This, however, does not cause operation of either of the compressors. As the temperature continues to rise, the mercury switch I43 of the thermostat I3I closes at 39 F. This causes operation of the compressor motor 63' provided the mercury switch I68 of the pressure responsive switching mechanism I60, which responds to the operation or non-operation of the circulating pumps, is closed. It should first be noted that power is always available for the motor mechanism 2I5 provided this mercury switch I68 is closed, by a circuit as follows: Line wire 230,

wire 23I, mercury switch I68, wire 232, wire 233, 1

contact 228, wire 238, wire 239, and relay coil I88 to ground "0. It will be noted that this relay coil cannot be energized in the event the mercury switch I 68 is in open circuit position. Energization of relay coil I 88 moves arm switch 204 into engagement with contact 205 whereupon electric heater I65 and relay coil I89, in series, are energized as follows: Line wire 230, wire 240, wire 24I, wire 242, contact 205, switch arm 204, wire 243, switch arm I62, switch arm I63, wire 244, wire 245, electric heater I66, wire 246, relay coil I89 to ground IIO. Energization of electric heater I65 starts heating the bimetallic element I64, as heretofore explained. Energlzation of relay coil I89 moves switch arms 201 and 208 into engagement with contacts 209 and 2 I0. Engagement of switch arm 201 with contact 209 energizes relay coil I86 as follows: Line wire 230, wire 23I, mercury switch I68, wire 232, wire 233, wire 236, mercury switch I43, wire 231, contact arm 226, contact 228, wire 238, wire 241, wire 248, switch arm 201, contact 209, wire 249, and relay coil I86 to ground IIO. Energization of this relay coil I86 energizes the compressor motor 63 and the condensing pump motor 11. The circuit for compressor motor 63 is as follows: Line wire 230, wire 240, wire 24I, wire 250, switch arm I96, contact I98, wire 25I, and compressor motor 63 to ground H0. The circuit for condenser pump motor 11 is as follows: Line wire 230, wire 240, wire 252, switch arm I91, contact I99, wire 253, and wire 254, to condenser pump motor 11 and ground 0.

It will thus be seen that a rise in the temperature of the chilled water to 39 F. causes energization of the heating element I65 and operation of the compressor motor 63 and the condenser pump motor 11. It will be noted that none of these devices could be energized or placed in operation, as the case may be, if the mercury switch I68 were not in closed position. In other words, it is impossible to energize the compressor or the condenser water pump in the event neither of the circulating pumps I3 or I4 is iii operation.

Qperation of the condenser water pump should cause circulation of the condenser water and reduce the pressure on the suction side of the pump I5. If this pump does operate and reduces this pressure, then the mercury switch N5 of the pressure responsive switching mechanism I6I will move to closed position. Closing of this mercury switch shunts the heating element I65 by a circuit as follows: From the upper end of heating element I65, wire 255, mercury switch I25, wire 256, and wire 245 to the lower end of heating element I 66. Shunting of this heating element operatively deenergizes the same whereupon no further heat is delivered to the bimetallic element I64. It will, therefore, be apparent that if this pressure is reduced quickly enough after the initial energization of heating element I65 so as to prevent suiiicient heating of bimetallic element I 64, the switch arms I 62 and I63 will not separate and the apparatus can remain in operation.

Assuming that the load on the apparatus is not particularly high at this time, the operation of compressor motor 63 will provide suflicient refrigeration to cool the chil ed water down to 35 F. In so doing, the water will pass through a temperature of 36 F. whereupon mercury switch I5I of the thermostat I32 will return to the position shown in Fig. 1 and cause a further half revolution of the motor mechanism 2I5. As explained' above, however, this will only serve to bring the motor mechanism 2I5 back to the position shown and the contact arm 226 will remain on the contact 228. When the temperature has thus been lowered to 35 F. the mercury switch I43 oi the thermostat I3I opens so as to deenergize the various relays whereupon the compressor motor 63 and-the condenser pump motor 11 are deenergized. The parts are, therefore, in the position shown in Fig. 1 except that contact arm 226 is engaging contact 228.

Since no refrigeration is now being furnished to the chilled water, its temperature will gradually rise. When it rises to 38 F. mercury switch I5I will again be operated so that its right-hand electrodes close. The motor mechanism 2I5 goes through a further half revolution and this time moves contact arm 226 back into engagement with contact 221. Upon a. still further rise to 39 F., mercury switch I43 will again close. This time, however, since the contact arm 226 is engaging the contact 221, the relay coil I81 will be energized instead of the relay coil I88. This circuit is as follows: Line wire 230, wire 23I, mercury switch I68, wire 232, wire 233, wire 236, mercury switch I43, wire 231, contact arm 226, contact 221, wire 260, wire 26I, and relay coil I81 to ground H0. It will again be noted that this relay coil cannot be energized unless the mercury switch I68 is in closed circuit position. Energization of relay coil I8I moves switch arm I into engagement with contact 202 to energize heating element I65 and relay coil I89 by a circuit as follows: Line wire 230, wire 240, wire 24I, wire 262, wire 263, wire 264, contact 202, switch arm 20I, wire 265, wire 243, switch arm I62, switch arm I63, wire 244, wire 245, heating element I65, wire 246 and relay coil I89 to ground IIO. This causes movement of switch arms 201 and'208 into engagement with contacts 209 and 2I0. Engagement of switch arm 201 with contact 209 will not cause energization of relay coil I86 as it did formerly since contact 226 is disengaged from contact 228, but engagement of switch arm 208 with contact 2I0 does cause energization of relay coil I85 as follows: Line wire 230, wire 23I, mercury switch I66, wire 232, .wire 233, wire 236, mercury switch I43, wire 231, contact arm 226, contact 221, wire 260, wire 266, wire 261, switch am 208, contact are and wire 268 to relay coil I85 and ground IIII. Energization of relay coil I85 moves switch arms I9I and I62 into engagement with contacts I63'and I96 to energize compressor motor 62 and condenser pump motor II. The circuit for compressor motor 62 is as follows: Line wire 230, wire 248, wire 24I, wire 262, wire 263, wire 268, switch arm I9I, contact I93, and wire 210 to compressor motor 62 and ground III]. The circuit for condenser pump motor 11 is as follows: Line wire 236, wire 24!], wire 24I, wire 262, wire 21I, switch arm I92, contact I94, wire 212, and wire 254 to condenser pump motor 11 and ground I I0. Operation of the condenser pump should cause a decrease in the pressure in pipe 16 as explained before to in turn cause closure of mercury switch I15. If this occurs in time, the heating element I65 is shunted before the switch arms I62 and I63 separate by reason of excessive heating of bimetallic element I64. It will be seen at this time, automatically, the compressor motor 62 has been energized instead of the compressor motor 63. In other words, consecutive demands for cooling have resulted in alternate operation of the compressors.

It will be noted that irrespective of which compressor is in operation, the relay coil I89 is energized. If it should happen that a single compressor is not able to prevent the temperature of 23I, mercury switch I68, wire 232, wire 213, mercury switch I35, wire 214, wire 248, switch arm 281, contact 289, wire 249, and relay coil I86 to ground II8. Energization of relay coil I86 energizes compressor motor 63 as heretofore explained. Also, closure of this mercury switch I establishes an energizing circuit for relay coil I85 as follows: Line wire 238, wire 23I, mercury switch I68, wire 232, wire 213, mercury switchl35, wire 215, wire 261, switch arm 288, contact 2 I 8, wire 268, and relay coil I85 to ground II8. Such energization of relay coil I85 energizes compressor motor 62 by the circuit set forth above. It is, therefore, seen that irrespective of which compressor may be in operation at the time, a rise in the chilled water temperature to 42 F. causes the other compressor to be placed in operation.

The two compressors are, of course, of such capacity as to lower the temperature of the cooling water regardless of the load. Since mercury switch I35 does not open until the temperature has fallen to 34 F., both of these compressors will continue to remain in operation even after mercury switch I43 moves to open position. Preferably, the mercury switches I35 and M3 should open at the same time but practically it is impossible to get this accurate a response in two different instruments, wherefor the mercury switch I35 has been indicated as opening at 34 F. and the mercury switch I43 as opening at 35 F.

From the. foregoing, it will be seen that the system of Fig. 1 can be utilized to provide either heated water or chilled water for circulation to any desired point of use and particularly to air conditioning devices for summer and winter cooling and heating. The arrangement is such that the chilled water can be circulated at one of two speeds depending upon the temperature of the chilled water being returned from the point of use. Furthermore, these two speeds are accomplished by using two clrculators, either of which can be placed into continuous operation and the other of which is automatically placed into operation upon such a rise of temperature of the returned chilled water. The system further prevents operation of the refrigeration system for cooling the water in the event neither of these circulators is in operation. In addition, the refrigeration system is caused to shut down if the condenser water pump does not come into operation within a predetermined time after the refrigeration system is placed in operation. This time delay is of particular utility where operation of the condenser water pump is measured by a change in the presure of the condenser water due to the fact of its circulation. The system of Fig. 1 further provides an arrangement in which a plurality of refrigeration devices are utilized and in which both can be operated simultaneously, or in which they are separately operated alternately upon subsequent and consecutive demands for .cooling.

Turning now to Fig. 2 of the drawings, while the supply of chilled and heated water which is provided by the apparatus described in connection with Fig. 1 can be used in any desired manner, I prefer to utilize it in connection with an air conditioning system which includes a plurality of air conditioning devices. Three of these air conditioning devices are indicated at 288, 28I and 282. These air conditioning devices are all located in a room 283 which is utilized as a mixing chamber or a controlling chamber by means of which fresh air- 'in the form of windows, for example.

or return air'is furnished to the various air conditioning devices 288, 28I and 282. provided with openings 284 and 285, which may be These openings 284 and 285 are defined by plates 286,281 and 288. Located between the plates 286 and 281, and disposed within the room 283, are dampers 289. These dampers 289 are each rotatably mounted upon shafts 298 and these dampers comprise the exhaust dampers for exhausting air from the room 283 when the fresh air dampers are open. In a similar manner, dampers 29I are pivoted on shafts 292 and are disposed between the plates 281 and 288. These dampers comprise the fresh air dampers and permit the taking into the room 283 of fresh air when they are open. The plate 281 is provided with an singularly-disposed extension 293. Also located within the room 283. is a partition 294 which runs substantially parallel to the ceiling 295 of the room. This partition 294 is provided with an extension 296 and a further extension 291. Disposed between the extension 296 of the partition 294 and the extension 293 of the plate 281 are dampers 298 each of which is pivotally mounted upon a suitable shaft 299. The space between the ceiling 295 and the partition 294 'is utilized for returning air from the various spaces conditioned by the air conditioning devices 288, 28I and 282 and the dampers 298 control the flow of this return air into the inlet ends of these various conditioning devices. Suitable baiile plates 388 and 38I may be respectively pivotally connected to the plate 288 and the extension 291 and positioned in such a manner as to properly baflle the return air or fresh air, as the-case may be. Located between these various sets of dampers and the air conditioning devices 288, 28I and 282 are suitable filters 382 which are supported by brackets 383 that permit the easy removal of these filters.

Referring now to both Figs. 2 and 3, the manner in which these various sets of dampers are controlled will now be explained. The fresh air dampers 29I are controlled by the main operating shaft 385 of a motor mechanism which may take any desired form. The connection between one of the fresh air dampers 29I and this main operating shaft 385 includes a crank 386 which is secured to the main operating shaft 385, and a connecting link 381 which connects this crank 386 to the damper. This damper and the other fresh air dampers are interconnected by links 388 by means of which all of the fresh air dampers are simultaneously moved in the same direction and to the same extent.

This main operating shaft 385 is operated by a reversible motor means which is herein shown as comprising a pair of motor rotors 389 and 3I8 which are secured to a common rotor shaft 3I I. Associated with the rotors 389 and 3I8 are field windings 3 I 2 and 3 I 3. The rotor shaft 3| I is connected to the main operating shaft 385 through suitable reduction gearing indicated generally at 3I4.

Energization of the field windings 3 I 2 and 3 I3 is controlled by a relay mechanism generally indicated at 3I5. This relay mechanism 3I5 includes an armature 3I6 which is pivoted at 3" and includes legs 3I8 and 3I9. Associated with the leg 3 I8 is a main relay winding 328 and an auxiliary relay winding 32I. In a similar manner, a

main relay winding 322 and an auxiliary relay winding 323 are associated with the leg 3I9 of the armature 3I6. Secured to the armature 3I6, through the medium of a piece of insulating mate- This room 283 is rial 324, is a switch arm 328 which is normally disposed intermediate a pair of contacts 326 and 321. Upon energization of the main relay winding 322 to a higher degree than that of main relay winding 320, armature 3|6 will be rotated counter-clockwise and switch arm 325 will move into engagement with contact 326. On the other hand, if the main relay winding 320 becomes more highly energized than the main relay winding 322, then armature 316 is rotated in a clockwise direction and switch arm 325.moves into engagement with contact 321.

The main relay windings 320 and 322 are connected in series across a source of power herein shown as the secondary 328 of a transformer 329 having a high voltage primary 338. This series circuit is as follows: Secondary 328, wire 33 l, wire 332, wire 333, main relay winding 320, wire334,

- wire 335, main relay winding 322, wire 336, wire 331, and wire 338 to the other side of secondary 328. In order to energize one or the other of these main relay windings more highly than the companion relay winding, two thermostats generally indicated at 340 and 34! are arranged to substantially short-circuit one or the other or these main relay windings under certain conditions.

The thermostat 340 includes a switch carrying arm 342 which is pivoted at 343 and supports a mercury switch 344. This switch carrying arm 342 is positioned by one end of a bellows 345, the other end of the bellows being fastened to a suitable support 346. The bellows 345 is charged with a suitable volatile fluid wherefor variable pressures are created therein upon variations in the temperature at the bellows 345 and these variable pressures are opposed by a coiled spring 341 which has one of its ends secured to the switch carrying arm 332 and its other end secured to the support 343. Mercury switch 343 is of the double circuit type which has a pair of electrodes in either end so that one or the other of the pairs of electrodes is bridged by the mercury contained in the mercury switch. In other words, the mercury switch 334 comprises a single-pole, double-throw switch. This thermostat responds to the temperature of the outdoor atmosphere and the arrangement is such that a circuit is closed through the electrodes in its right-hand end whenever the outdoor tem-' perature is at or above 60 F. Whenever the outdoor temperature falls below this value the mercury switch 334 is tilted in the opposite direction so that the circuit through the right-hand electrodes thereof is broken but a circuit is established through its left-hand electrodes.

The thermostatic switch 34| diiiers from the thermostatic switch 340 only in that it is set to operate at a different temperature. This thermostat 341 includes a switch carrying arm 348 which is pivoted at 349 and supports a mercury switch 356. This switch carrying arm 348 is positioned by one end of a bellows 35l, the other end of which is secured to a suitable support 352. The bellows 35| is also charged with volatile fluid so that varying pressures are created therein upon temperature changes in the bellows and these variable pressures are opposed by a coiled spring 353 which has one of its ends secured to the switch carrying arm 348 and its other end secured to the support 352. This mercury switch- 350 is also of the double circuit type. This thermostat likewise responds to the temperature of the outside air and the setting of the thermostat is such that the right-hand electrodes of the mercury switch are closed whenever the outside temperature is at or above 70 F, I f the outside temperature falls to a value below 70 F., the mercury switch 350 is tilted in the opposite direction and opens a circuit through the right-hand electrodes while closing a circuit through the left-hand electrodes.

As stated above, th so two thermostats cooperate in controlling the relative energizations of the main relay windings 320 and 322. For the purpose of again equalizing the energizations of these two main relay windings, the main operating shaft 305 operates a balancing contact arm 354 which cooperates with a balancing resistance 355. With the parts in the position shown, the outside temperature is above. 70 F., wherefor a circuit is closed through the right-hand electrodes of each of the mercury switches 344 and 350 of the thermostats 340 and 34L As a result, the main relay winding 322 is substantially shortcircuited as follows: From the upper end of main relay winding 322, wire 335, wire 356, wire 351, the right-hand electrodes of mercury switch 344, wire 358, the right-hand electrodes of mercury switch 35!), wire 353, wire 360, a protective resistance 361, wire 362 and wire 336 to the lower end of main relay winding 322. This short circuit of the main relay winding 322 would be complete were it not for the protective resistance 36L Also, with the parts in the position shown, the fresh air dampers are completely closed and the balancing contact arm 354 is engaging the extreme left-hand end of balancing resistance 355. Under these conditions, the main relay winding 320 is substantially short-circuited by a circuit as follows: From the upper end of main relay winding 320, wire 334, wir 356, wire 363, balancing contact arm 353, wire 364, wire 336, a protective resistance 361, wire 368 and wire 333 to the lower endof main relay winding 320. Here again, complete short-circuiting is prevented by reason of the protective resistance 361. Were it not for these protective resistances 36l and 361, it will be apparent that the secondary 328 of the transformer would be completely short-circuited. These protective resistances prevent such complete short-circuiting so that a small amount of current flows through the main relay windings 323 and 322. The two protective resistances are equal in value whereior the main relay windings were equally energized. As a result, the armature 3H3 is in the intermediate position shown wherein switch arm 325 is disposed between contacts 326 and 321 and is not engaged with either of them.

Assuming that the outdoor temperature should fall below 70 F. but still remain above 60 F., it will be apparent that such outdoor air could well be used in the air conditioning devices since it is of an intermediate temperature. If this should occur, the mercury switch 344 remains in the position shown in Fig. 3 but the mercury switch 350 moves to its opposite circuit closing position wherein a circuit is completed through its left-hand electrodes. This change in circuit connections removes the substantial short-circuit for the main relay winding 322, which was traced above, and establishes an additional substantial short-circuit for the main relay winding 320. This new circuit is as follows: From the upper end of main relay winding 320, wire 334, wire 356, wire 351, right-hand electrodes of mercury switch 344, wire 358, left-hand electrodes of mercury switch 350, wire 369, wire 366, protective resistance 361, wire 368, and wire 333 to the lower end of main relay winding 320. The main relay winding 322 is now considerably more highly ensecondary 328. The energization of auxiliary relay winding 323 exerts an additional pull on the leg 3l9 of armature 3!6. In this particular apparatus this auxiliary winding is not necessary but the motor mechanism used herein is a standard one of general application which is normally controlled by a resistance type of control rather than by on and off switches and this auxiliary pull is utilized to increase the contact pressure upon light engagement of this switch arm and the contact 326 when the motor mechanism is variably controlled by such variable resistance controller. The energization of field winding 3l2 causes rotation of main operating shaft 305 in such a direction that the fresh air dampers 29! are moved towards open position and the balancing resistance 355 towards the right-hand end. As the balancing contact arm 354 moves along the balancing resistance 355, the original substantial short-circuit traced for main relay winding 320 is gradually removed by reason of the inclusion therein of part of the balancing resistance 355. However, this main relay winding 320 remainssubstantially Ishortcircuited by reason of the second shunt circuit which was established upon movement of mercury switch 350 to its position wherein a circuit was completed through its left-hand electrodes. When the main operating shaft has been moved sufficiently far that balancing contact arm 354 engages the extreme right-hand end of balancing resistance 355, a substantially, complete short circuit for the main relay winding 322 is established as follows: From the upper end of main relay winding 322, wire 335, wire 356, wire 363, balancing contact arm 354, wire 314, wire 360, protective resistance 36!, wire 362 and wire 336 to the lower end of main relay winding 322. The energization of these main relay windings are again thus equalized and the extra pull of auxiliary relay winding 324 is not sufiicient to maintain switch arm 325 in engagement with contact 326. These parts, therefor, slightly separate and interrupt the circuit through the auxiliary winding 323 and the field winding 3l2. Deenergization of the auxiliary relay winding 323 enables switch arm 325 to move further from the contact 326. The main operating shaft 305 ceases rotating upon deenergization of the field winding 3l2 and remains in its new position. This position of the main operating shaft 305 wherein the balancing contact arm 354 engages the extreme right-hand end of balancing resistance 355 is such that the fresh air dampers 29! have been moved to a full open position.

If the outside temperature should again rise to above 70 F., the parts would be restored to the position shown in Fig. 3 wherein the fresh air dampers are completely closed. On the other hand, if the outside temperature should continue to drop and falls to below 60 F., then not only the mercury switch 350 would be tilted so that a circuit is closed through its left-hand electrodes, but the mercury switch 344 would also be tilted in a similar manner so that a ci u t heretofore explained.

switches is well known in the art and no furtheris completed through its left-hand electrodes. Under these conditions the short circuit of winding 320 is opened, and a substantially complete short circuit for main relay winding 322 is established as follows: From the upper end of main relay winding 322, wire 335, wire 358, wire 351, left-hand electrodes of mercury switch 344, wire 315, protective resistance 36!, wire 362, and wire 336 to the lower end of main relay winding 322. Main relay winding 320 is now more highly energized than main relay winding 322 wherefor armature 3!6 is rotated in a clockwise direction and switch arm 325 moves into engagement with contact 321. This establishes a series circuit through the auxiliary relay winding 32! and the field winding 3l3. This circuit is as follows: Secondary 328, wire 33!, wire 310, switch arm 325, contact 321, wire 316, auxiliary relay winding 32!, wire 311, field winding 3!3, wire 313, and wire 338 to the other side of secondary 328. The energization of auxiliary relay winding 32! exerts an additional pull on leg 3!8 of armature 3!6 so as to move switch arm 325 into more firm engagement with contact 321. Energization of field winding 3!3 causes rotation of main operating shaft 305m 9. direction opposite to that in which it was rotated by the energization of field winding 3l2. In other words, fresh air dampers 29! are moved back towards their closed position and the balancing contact arm 354 moves along balancing resistance 355 towards its left-hand end. When the main operating shaft 305 has thus been rotated sufficiently far to move balancing contact arm 354 to the extreme left-hand end of balancing resistance 355, as shown in Fig. 3, the fresh air dampers will again be completely closed and the first mentioned substantially complete short circuit for the main relay winding 320 will again be established. The main relay windings 320 and 322 are, therefore, again equally energized and the pull of auxiliary winding 32! is not sufficient to maintain switch arm 325 in engagement with contact 321. These parts therefore separate, and deenergize the auxiliary relay winding 32! and the field winding 3l3. Deenergization of the auxiliary relay winding 32! enables a wider separation of the switch arm 325 and the contact 321. Deenergization of the field winding 3l3 causes main operating shaft 305 to cease its rotation.

As a practical matter, the limits of movement of main operating shaft 305 to fresh air damper open position and fresh air damper closed position would be obtained by the use of limit switches rather than through the balancing out process The use of such limit description thereof is thought necessary herein.

From the foregoing it will be seen that the fresh air dampers are closed whenever the outside air temperature is above a certain value or is below a lower predetermined value. These values, for the purposes of explanation, have been selected as '10 F. and 60 F.

Whenever the fresh air dampers are closed it is desired to have the return air dampers open and whenever the fresh air dampers are open it is desired to have the return air dampers closed. In other words, this invention contemplates that either fresh or return air will be furnished to the air conditioning devices 280, 28!, and 282. In order to accomplish this, the main operating shaft 305 operates a variable resistance controller which in turn controls the return air dampers through a m t r mechanism which will now be described.

2,177,eoa

This variable resistance controller comprises a control arm 388 which is operated by the main operating shaft 388 and which cooperates with a control resistance 38!. The arrangement is such that the control arm 388 engages the extreme right-hand end of control resistance 38! when the main operating shaft 385 is in such position that the fresh air dampers are completely closed and engage the extreme left-hand end of this control resistance 38! when the main operating shaft 385 is in such position that the fresh air dampers are completely open.

This controller comprised by the control arm 388 and control resistance 38! controls a relay mechanism generally indicated at 382. This relay mechanism 382 is in all respects similar to the relay mechanism 3l5 heretofore described. In other words, it includes an armature 383 which is pivoted at 384 and is provided with legs 385, and 388. Cooperating with the leg 385 is a main relay winding 381 and an auxiliary relay winding 388.] Likewise, a main relay winding 389 and an auxiliary relay winding 398 cooperate with the leg 388 of the armature 383. A switch arm 39! is secured to the armature 383 through the medium of a piece of insulating material 392. This switch arm is normally disposed between a pair of contacts 393 and 394. The main relay windings 381 and 389 are connected in series across any suitable source of power such as the secondary 395 of a step-down transformer 398 which is provided with a high voltage primary 391. This series circuit is as follows:' Secondary 395, wire 398, wire 399, wire 488, main relay winding 381, wire 48!, wire 482, main relay winding 389, wire 483, wire 484, and wire 485 to the other side of secondary 395. v

This relay mechanism 382 controls the energization of a reversible motor means which is herein shown as comprising two oppositely acting motors. One of these motors comprises a rotor 488and a cooperating field winding 481 and the other comprises a rotor 488 and a cooperative field winding 489. These two motor rotors are secured to a common rotor shaft 4l8 which is connected to a main operating shaft 4! through reduction gearing generally indicated at 4!2. This main operating shaft 4!! operates a crank 4!3 which is connected to one of the return air dampers 298 by means of a link M4. The remaining fresh air dampers 298 are interconnected by links 5 so that all of these return air dampers move simultaneously in the same direction and to the same extent.

The controller comprised by the control arm 388 and the control resistance 38! is adapted to gradually vary the respective energizations of the main relay winding 381 and 389 in a manner which will be explained hereinafter. In order to rebalance the energizations of these main relay windings, whenever they are unbalanced, the main operating shaft 4!! operates a balancing contact arm 8 which cooperates with a balancing resistance 4!1.

With the parts in the position shown, the con-- trol arm 388 is engaging the extreme right-hand end of control resistance 38! wherefore main relay winding 389 is substantially completely short-circuited by a circuit as follows: From the upper end of. main relay winding 389, wire 482, wire 4!8, wire 4|9, control arm 388, wire 428, wire 42!, a protective resistance 422, wire 423, and wire 483 to the lower end of main relay winding 389. The main relay winding 381 is also substantially completely short-circuited by a circuit as follows: From the upper end of main relay winding 381, wire 48!, wire 4!8, wire 424, balancing contact arm 8, wire 425, wire 426, a protective resistance 421, wire 428, and wire 488 to the lower end of main relay winding 381. These two protective resistances are equal so it will be apparent that under these conditions the main relay windings 381 and 389 are equally energized. The switch arm 39! is therefore disposed intermediate contacts 393 and 394 and is not engaging either of them. The main operating shaft 4!! is stationary and in such position that the return air dampers 298 are all in open position.

If the fresh air dampers 28! should now start to move towards open position by reason of proper rotation of main operating shaft 385 as a result of change in outdoor temperature as explained above, control arm 388 will begin to move along control resistance 38! towards its left-hand end. Such movement of the control arm 388 gradually inserts all of the control resistance 38! in the shunt circuit just traced for the main relay winding 389. This renders the short circuit for the main relay winding 389 less complete so that less current flows through the short circuit or shunt and more flows through the main relay winding 389. When this increased current flow through the main relay winding 389 becomes sufficiently high the armature 383 will be rotated in a counter-clockwise direction far enough to bring switch arm 39! into contact with contact 393. When this occurs, the auxiliary winding 398 and field winding 481 are energized in series by a circuit as follows: Secondary 395, wire 485, wire 429, switch arm 39!, contact 393, wire 438, auxiliary relay winding 398, wire 43!, field winding 481, wire 432 and wire 398 to the other side of secondary 395. This energization of field winding 481 causes rotation of main operating shaft 4!! in such direction that the balancing contact arm M8 moves towards the rght-hand end of balancing resistance M1 and the return air dampers 298 are moved towards closed position. The initial engagement of switch arm 39! with contact 393 was very light, but the energization of the auxiliary relay winding 398 created an additional pull on the leg 386 of ar mature 383 by means of which switch arm 39! is held more firmly in engagement with contact 393.

This movement of balancing contact arm 4H5 towards the right-hand end of balancing resistance 4H gradually inserts part of the balancing resistance 4!! into the short circuit or shunt circuit for the main relay winding 381. As a result, more current flows through the main relay winding 381 but at the same time the control arm 388 is continuing to move along control resistance 38! towards its left-hand end so that at all times the main relay winding 389 is energized more highly than the main relay winding 381. When the control arm reaches the center of control resistance 38! and the balancing contact arm 4l6 reaches the center of balancing contact 4I1 these main relay windings will be energized at the highest value that they are ever energized. As these two arms continue their movements the energization of these main relay windings thereupon decreases but the main relay winding 389 is always more highly energized than the main relay winding 38'! until a limiting position is reached. By the time the fresh air dampers have been completely opened, the control arm 388 has reached the extreme left-hand end of control resistance 38!. When this occurs, a new substantially complete short circuit for main relay winding 38! is established as follows: From the upper end of main relay winding 381, wire 48|, wire 8, wire 9, control arm 388, wire 433, wire 426, protective resistance 421, wire 428, and wire 488 to the lower end of main relay winding 381. Main relay winding 389 remains more highly energized than main relay winding 38! until the main operating shaft 3 has moved balancing contact arm 8 into engagement with the extreme right-hand end of balancing resistance 4| I. When this occurs, a new substantially complete short circuit is established for the main relay winding 389 which is as follows: From the upper end of main relay winding 389, wire 482,

wire 4|8, wire 424, balancing contact arm 8, wire 434, wire 42|, protective resistance 422, wire 423 and wire 483 to the lower end of main relay winding 389. The main relay windings 381 and 389 are now equally energized and the pull exerted by the auxiliary winding 398' is not sumcient to maintain switch arm 39| into engage- ,ment with contact 383. These parts, therefore,

separate and interrupt the series circuit through the auxiliary winding 398 and the field winding 481. Deenergization of theauxiliary relay winding 398 permits the switch arm 39| to move further away from the contact 393. Further rotation of main operating shaft 4| I ceases, of course, upon deenergization of field winding 481. Under these conditions, the return air dampers 298 are completely closed.

Whenever the outdoor conditions change again so as to close'the fresh air dampers 29| the control arm 388 will begin moving away from the left-hand end of. control resistance 38| and will move towards its right-hand end. This will increase the energization of main relay winding 38! in respect to the energization of main relay winding 389, in a manner which should now be apparent. Armature 383, therefore, rotates in a clockwise direction and switch arm 39| will engage contact 394. This establishes a circuit through the auxiliary relay winding 388 and the field winding 489 as follows: Secondary 395, wire 485, wire 429, switch arm 39I, contact 394, wire 435, auxiliary relay winding 388, wire 438, field winding 489, wire 432 and wire 398 to the other side of the secondary 395. Main operating shaft 4| I is now rotated in the opposite direction so that return air dampers 298 begin moving towards open position and the balancing contact arm 4| 8 begins moving away from the righthand end of balancing resistance 4|| and towards its left-hand end. Energization of the auxiliary relay winding 388 increases the contact pressure between the switch arm 39l and contact 394 as previously explained in connection with contact 393. The main operating shaft 4 will continue rotating in this new direction until the' parts return to the position shown in Fig. 3 wherein the control arm 388 is engaging the extreme right-hand end of control resistance 38| and the balancing contact 8 is engaging the extreme left-hand end of balancing resistance 4| 1. When these positions are again assumed the main relay windings 381 and 389 will again be equally energized and the switch arm 39| will disengage contact 394 to deenergize the auxiliary relay winding 388 and the field winding 489. Further movement of the main operating shaft 4 ceases and the return air dampers are now again in their full open position.

As in the case of the motor mechanism which controls the fresh air dampers 29| these end or the exhaust dampers 289 in order that the air returning from the air conditioning devices may be exhausted to the atmosphere. This is accomplished byhaving the main operating shaft 4 operate a control arm 448 which cooperates with a control resistance I. These parts are connected to a motor mechanism 442 by means of wires 443, 444 and 445. Power is supplied to this motor mechanism 442 by line wires 448. This motor mechanism 442 is provided with a main operating shaft 441 which operates a crank 448. This crank 448 is connected to one of the exhaust dampers 289-bit means of a link 449. All of the exhaust dampers 289 are interconnected by means oflinks 458 so that all of them move in the same direction and to the same extent. In viewof the foregoing description of the manner in which the return air dampers are controlled, it is now thought that it will be obvious how the movement of control arm 448 in respect to the control resistance 4, as a result of rotation of the main operating shaft 4| controls the motor mechanism 442 so as to open and close the exhaust dampers 289 upon closing and opening of the return air dam'pers 298.

From the foregoing it will be seen that whenever the outside air temperature is above 70 F., the fresh air dampers and the exhaust dampers are closed and the return air dampers are open. This means that the air being taken out of the spaces to which conditioned air is being supplied will be returned to the air conditioning devices for reconditioning. If the outdoor temperature falls below 70 F. but remains above 60 F., the fresh air dampers and the exhaust dampers are opened and the return air dampers are closed.

This means that fresh air is delivered to the air conditioning devices and the air being withdrawn from the spaces being conditioned, instead of returning to the air conditioning devices for reconditioning, is exhausted into the outside atmosphere. If the outdoor temperature continues to drop so that it falls below 60 F., then the parts are returned to the position shown wherein the return air dampers are open'so that return air is again used for conditioning purposes instead of fresh air. v

It will be noted that although these dampers are all controlled in an on and off manner, motor mechanisms of the type which generally give a modulating or variable movement have been utilized. The reason for this arrangement is that the ordinary commercial two-position motor mechanisms are provided with auxiliary switches that are onlyoperated when the motor mechanism reaches an extreme position. In this instance, it would mean that the fresh air dampers would have to completely open before the motor mechanism for operating the return air dampers would be placed in operation. In turn, the return air dampers would have to completely close before the exhaust dampers would begin to open. These motor mechanisms necessarily operate relatively slowly in order to develop the necessary force and if ordinary two-position motors were utlized and equipped with auxiliary switches so that one was operated by another then it will be obvious that a considerable delay wouldobtain between a demand for a change between the position of one of the dampers and the time when all of them would be so changed.

On the other hand, it is desirable to use this so-called "dual control" wherein one motor mechanism causes a second motor mechanism to operate in a manner similar to which the first motor mechanism has been operated in that only one set of control thermostats is necessary, it often being impossible to use one set of controlling thermostats to directly control a plurality of motor mechanisms by connecting them up in parallel since many of the standard motor mechanisms on the market cannot be hooked up in parallel. A relay would, therefore, have to be interposed to use such a system. Again, if the motor mechanism could be hooked up in parallel it is possible that the placing of such a large number of motor mechanisms under the control of a single set of controlling thermostats would require so much power as to exceed the rating of the thermostats. In the presentarrangement, motor mechanisms of the proportioning or modulating type are used which are ordinarily provided with auxiliary potentiometers in order to give a dual control. As pointed out in the above explanations, as soon as the motor mechanism which controls the fresh air dampers begins to operate the fresh air dampers, it also begins to operate the dual potentiometer. This means that the return air dampers begin to move to their new position as soon as the fresh air dampers begin to move. In turn, the exhaust dampers also begin to move just as soon as the return air dampers begin to move. The present system, therefore, makes it possible to have all of these sets of dampers moving at the same time wherefor the time delay between a demand for a shift in damper position and the time such shift actually occurs in all of the dampers is greatly reduced. Of course, in smaller systems, wherein the number of dampers is less and wherein they are of less weight and therefore require less power, a single motor mechanism can be used and mechanically interconnected to all of the dampers in such a manner as to give the desired results, but the present system, as will be seen, is concerned with a large installation wherein the dampers are numerous and are heavy and by this system substantially simultaneous movement of all of the dampers can be obtained, although a plurality of motor mechanisms are employed and this is obta ned without the utilization of a plurality of sets of controlling thermostats or the interposition of a relay between a single set of thermotats and the plurality of motor mechanisms.

Returning now to Fig. 2 of the drawings, each of the air conditioners 280, 28! and 282 is provided with a combined heating and cooling coil, these coils being indicated at 460, 46f and 462. The pipe l0 which delivers-the heated or chilled water from the circulating pumps l3 and I4 is connected to each of these combined heating and cooling coils in any desired manner. In this diagrammatic showing of the invention, the pipe I0 is shown connected to a four-way connection 463 from. which pipes 464, 465 and 466 lead. The pipe 464 connects to the cooling and heating coil 460 and the pipes 465 and 466 are adapted to be connected to the cooling and heating coils 461 and 462. In the case of each of these conditioners, the combined heating and cooling coil does not extend all the way to the bottom of the conditioner but only extends to partitions indicated at 461, 468 and 469. These partitions form two passage ways through each conditioner, the lower passage of each of which comprises a by-pass passage. In the case of the conditioners 280 and 28!, an additional partition in each, which are indicated at 410 and 41!, provides for the passage of a relatively large amount of air through the combined heating and cooling coils and also provides auxiliary passages by means of which a relatively small amount of air can passthrough the heating and cooling coils. Located in this auxiliary passage of the conditioner 280 is a damper 412 which is pivoted upon a shaft 413.

Located in the main passage of this conditioner are face dampers 414 which are pivoted on shafts 415. These dampers 415 are interconnected by means of a link 416 so that they both move in the same direction and to the same extent. Located in the by-pass passage is a by-pass damper 411 which is pivoted on a shaft 418. The damper 411 is connected to one of the dampers 414 by means of a link 419, the arrangement being such that the damper 411 moves to the same extent as the dampers 414 but in an opposite direction. In other words, as the face dampers 414 move towards open position the by-pass damper 411 moves towards closed position and vice versa.

As indicated above, the air conditioner 28! is exactly the same as the air conditioner 280 and it includes an auxiliary damper 480 which is mounted in the auxiliary passage thereof and. is pivoted on a shaft 48!. It also includes a pair of face dampers 482 which are located in the main passage-way and are pivoted on shafts 483. These face dampers are interconnected by a link 484 in such a manner that they move in the same direction and to the same extent. Located in the by-pass passage is a by-pass damper 485 which is pivoted on a shaft 486. This by-pass damper 485 is connected to one of the face dampers 482 by a link :81, the arrangement being such that the by-pass damper 485 moves to the same extent as the face dampers 482 but in the opposite direction.

Located in the main passage of the air conditioner 282 are a plurality of face dampers 488 which are pivoted on shafts 489. These face dampers are interconnected by links 490 in such manner that they move in the same direction and to the same extent. Also located in the bypass chamber are by-pass dampers 49! which are pivoted on shafts 492. These dampers are interconnected by a link 493 and one of them is connected to one of the face dampers 489 by a link 494 in such manner that the face dampers and the by-pass dampers move the same amount but in opposite directions. The partition 469 of this conditioner 282 is provided with an opening in which is located a normally closed auxiliary damper 495 that is pivoted upon a shaft 496.

The heated or chilled water, after flowing through the combined heating and cooling coil 460, passes by way of a pipe 500' to a four-way connection 50l. Similarly, the water passing out of the combined heating and cooling coils 46| and 462 also return to this same four-way connection 50! by means of pipes 502 and 503. The main return pipe 20' is also connected to this four-way fitting 50 l.

Each conditioner is provided with a water spray for the purpose of raising the humidity of the air being conditioned in the winter as will. be explained hereinafter. These sprays are indicated at 504, 505 and 506. The spray 504 is shown connected to a spray water pipe 501 which includes an electrically operated valve 508 by means of which the supply of spray water may be turned on and off. The sprays 505 and 506 should be similarly provided with a supply of spray water and a controlling valve.

These three conditioners are respectively provided with fans which are operated by fan motors 569, 5Ifl and 5. These fans serve to pull air through their associated conditioners, which air will. be either return air or fresh air' as determined by the outdoor thermostats as explained in connection with Fig. 3, and deliver this air to various zones or spaces to be conditioned. These fans are controlled under certain conditions by a thermostat having an element 5|2 which responds to the temperature of the water leaving all of the various air conditioning devices and is herein shown as applied to the main return pipe 20. This thermostatic element 5| 2 operates a mercury switch 5l3 and moves the same to open circult position whenever the temperature of the return water falls below 90 F. For all temperature values above 90 F. this switch is closed; This switch is used during cold weather operation when the apparatus is utilizing hot water and it will be obvious that during summer operation when cold water is used the mercury switch 5I3 will be continuously open. The various fans are also controlled by a single-pole, double-throw switch which includes a switch arm 5l4, a winter contact 5l5 and a summer contact 5l6. Power is supplied by line wires 5" and 5l8, the latter being connected to ground lllll. The switch arm 5l4 is shown engaging the summer contact 5l 6 and under these conditions all of the fan motors are continuously energized by circuits as follows: Line wire 5", wire 5l9, switch arm 5l4, summer contact 5I6, wire 520 and wire 52l, at which point the circuit branches and goes in three directions. The first branch goes by way of wire 522 to the fan motor 509 and to ground H0, The second branch goes by way of wire 523 and wire 524 to fan motor 5! and to ground H0. The third branch goes by way of wire 523 and wire 525 to fan motor 5 and ground It will, therefore, be seen that during summer operation all of the fans of the various air conditioners are in continuous operation.

For winter operation the manual switch SM is moved into engagement with winter contact 5. A new circuit is then established for the various fan motors which is operative to energize these fan motors only in the event the temperature of the return water is above 90 F. It will be noted that this circuit goes from line wire 5", wire 5I9, switch arm 5l4, winter contact 5l5, wire 526. mercury switch 5|3 and wire 521 back to wire 52!, at which point the circuits for the various fan motors are as described above. As a result, during the winter the fan motors are only in operation provided the temperature of the return water is above 90 F. Under ordinary circumstances, the temperature of this water will always be above 90 F. and the purpose of this mercury switch 5I3 is for shutting down the fans under extraordinary conditions.

As noted above, the air conditioners 280 and 28l are exactly the same. It will be noted that the air conditioner 282 differs somewhat from these other two air conditioners. However, the control systems for the air conditioners are exactly the same and the results obtained by these two types of air conditioners are substantially the same although they are accomplished in different manners.

Referring now to both Figs. 2 and 4, the manner in which these air conditioners are controlled will now be explained. The face and by-pass dampers are operated by a motor mechanism that includes a main operating shaft 536 which is coupled to a rotor shaft 53! through suitable reduction gearing indicated generally at 532. This rotor shaft is operated by a reversible motor means which herein takes the form of two oppositely acting motors, one of which comprises a rotor 533 and associated field winding 534 and the other of which comprises a rotor 535 and an associated field winding 536. Energization of these field windings is controlled by a relay mechanism generally indicated at 531 which includes an armature 538 that is pivoted at 539 and is provided with a pair of legs 546 and 5. Associated with the leg 540 is a main relay winding 542 and an auxiliary relay winding 543. In a similar manner, a main relay winding 544 and an auxiliary relay winding 545 are associated with the leg 54! of the armature 538. Secured to this armature 538 is a switch arm 546 which is secured thereto through the medium of a block of insulating material 541. This switch arm 546 is normally disposed intermediate a pair of contacts 548 and 549 but does not normally engage either of them. The main relay windings 542 and 544 are connected in series across a suitable source of power indicated herein as the secondary 550 of a transformer 55! having a high voltage primary 552, which is connected to suitable line wires 553 and 554. This circuit is as follows: Secondary 556, wire 555, wire 556, wire 551, main relay winding 542, wire 558, wire 559, main relay winding 544, wire 560, wire 56l, and wire 562 back to the other side of secondary 550. In the absence of any other electrical circuits it will be obvious that these two main relay windings will be equally energized at all times so that the armature 538 will assume the position shown in Fig. 4 wherein switch arm 546 is disposed intermediate contacts 548 and 545 but is not engaging either one of them.

The energizations of these main relay windings 542 and 544 are primarily unequalized or unbalanced by a space temperature responsive thermostat generally indicated at 563. This thermostat can respond to the space temperature of the particular space which is being conditioned by an air conditioner to which the control system of Fig. 4 is applied or could respond to the temperature of the air being withdrawn from such space. This thermostatic mechanism 563 includes a bell crank pivoted at 564 and which is provided with a control arm 565, a corrector arm 566 and an actuating arm 561. The control arm 565 cooperates with a control resistance 568 and the corrector arm 566 cooperates with a corrector resistance 569. One end of a bellows 51llengages the actuating arm 561 and its other end is secured to a suitable support 51l. The bellows 516 is charged with a suitable volatile fluid so that variable pressures are created therein upon temperature changes and these variable pressures are opposed by a coiled spring 512 which has one of its ends secured to the actuating arm 561 and its other end secured to the support 51!.

The energization of these main relay windings 542 and 544 are also additionally varied by a space relative humidity responsive device generally indicated at 513. This device includes a bell crank pivoted at 514 which is provided with a control arm 515 and an actuating arm 516. The control arm 515 cooperates with a compensating resistance 511. A relatively humidity responsive element 518 has one of its ends secured to the actuating arm 516 and its other end secured to a suitable support 519. A coiled spring 580 has one of its ends secured to the actuating arm 516 and its other end secured to a suitable support 58! and serves to maintain the relative humidity responsive element 518 under proper tension at all times. This relative humidity responsive device 513 also includes an auxiliary on and off switch. This is indicated as being constituted by a switch carrying arm 582 which is pivoted at 583 and which carries a mercury switch 584. In operation, when the value of the relative humidity to which the element 518 responds rises to such a degree that the control arm 515 moves to the extreme left-hand end of compensating resistance 511, the actuating arm 516 engages the switch carrying arm 582 and lifts the same about its pivot 583 so as to tilt mercury switch 584 to a position opposite that shown in Fig. 4, wherefor a circuit is closed therethrough.

The energization of these main relay windings 542 and 544 are additionally modified by an outside temperature responsive controller generally indicated at 585. This controller includes a bell crank pivoted at 586 which includes a control arm 581 and a compensating resistance 588 with which such control arm is associated. The bell crank further includes an actuating arm 589 which is positioned by one end of a bellows 598, the other end of which is secured to a suitable support 59!. The bellows 598 is charged with a suitable volatile fluid so that variable pressures are created therein upon temperature fluctuations and these variable pressures are opposed by a coiled spring 592 which has one of its ends secured to the actuating arm 589 and its other end secured to the support 59I. This outdoor temperature responsive thermostat can be located out of doors or could be located in any other suitable position so that it responds to outdoor temperature changes.

Regardless of the manner in which the energizations of these main relay windings 542 and 544 are unbalanced, they are adapted to be rebalanced by means of a balancing potentiometer which includes a balancing contact arm 593 that is driven by the main operating shaft 538 and which cooperates with a balancing resistance 594.

During the winter operation, the energizations of these main relay windings 542 and 544 are adapted to be varied by a space temperature responsive thermostat generally indicated at 595. This thermostat includes a bell crank pivoted at 596 which is provided with a control arm 591 and an actuating arm 598. The control arm 591 cooperates with a control resistance 599. The actuating arm is positioned by a bellows 688, one end of which engages the actuating arm 598 and the other end of which is secured to a suitable support Bill. The bellows 688 is charged with a suitable volatile fluid and the variable pressures created therein upon temperature change are opposed by a coiled spring 682 which has one of its ends secured tothe actuating am 598 and its other end secured to the support 68!.

In order to selectively place this thermostat 595 in control of the relay mechanism 531 or to place the two thermostats 563 and 585 and the relative humidity responsive device 513 in control thereof, a triple-pole, double-throw switch is utilized which is generally indicated at 683. This switch is herein shown as manually operated, although it will be understood that it could be automatically operated if desired. This switch includes three switch arms 684, 685 and 686. When the switch is placed in summer position the switch arms 684, 685 and 686 respectively engage contacts 681, 688 and 689. When it is placed in wintei position, the switch arms respectively engage contacts BID, 6 and M2. nly two of the switch arms of this switching mechanism 683 are utilized for varying the control of the relay mechanism 531 and the other switch arm thereof is utilized to control certain other portions of the system which will be described later.

The lower end of main relay winding 542 is connected to the switch arm 685 by a wire 613 and the lower end of main relay winding 544 is similarly connected to the switch arm 684 by a wire 6. The summer contact '681 which cooperates with the switch arm 684 is connected to the left-hand end of each of the resistances 588, 511 and 568 by wires H5, H6 and 611. The summer contact 688 which cooperates with the switch arm 685 is connected to the right-hand end of each of these resistances by means of wires M8, M9 and 628. The winter contact M8 is connected to the left-hand end of the control resistance 599, by means of a wire 622. Likewise, the winter contact 6 is connected to the right-hand end of this control resistance 599, by a wire 625. The center of corrector resistance 569 is connected to the junction of wires 558, and 559, and, therefore, connected intermediate the main relay windings 542 and 544, by means of wires 621, 628, 629' and 638. The control arm 515 is likewise connected intermediate'these main relay windings by being connected to the junction of wires 621 and 628, through a rheostat 63l, by means of wires 632 and 633. The control arm 581 is similarly connected to the junction of wires 628 and 629, through a rheostat 634, by means of wires 635 and 636. The control arm 591 is directly connected intermediate these main relay windings by being connected to the junction of wires 629 and 638, through a protective resistance 623 by wires 624, 631 and 638. The balancing contact arm 593 is connected to the junction of wires 631 and 638, through a rheostat 639, by means of wires 648 and SM. The opposite ends of the balancing resistance 594 are connected across the secondary 558 by a wire 642 which connects to the junction of wires 56l and 562 and by a wire 643 which connects to the junction of wires 555 and 556.

Assume that the switch 683 is in its summer position. Also, assume that the indoor temperature responsive device 563 has a range of 15 F. to 98 F., that the outdoor temperature responsive mechanism 585 has a range of from 75 F. to 105 F. and that the relative humidity responsive control 513 has a. range of from per cent to 60 per cent. with the parts in the position shown, the temperature of the space being controlled is substantially 82 F., the outside temperature is substantially 90 F., and the relative humidity of the space is substantially 45 per cent. The control arms of the three controllers are, therefore, engaging the center of their associated resistancesand, in order to maintain the main relay windings 542 and 544 equally energized, the balancing contact arm is in the middle of balancing resistance 594 wherefor the main operating shaft 538 is intermediate its limits of motion.

If the inside temperature should rise, the control arm 565 will move along control resistance 568 towards its left-hand end. Such movement of this control arm will reduce the energization of main relay winding 544 in respace to the energization of main relay winding 542 whereupon armature 538 will be rotated in a clockwise direction and switch arm 546 will gradually move towards contact 548. When this rise in space 

